1. Field of the Invention
The invention resides in the field of analytical spectrometers and more particularly relates to devices for transporting and manipulating a sample for presentation to the optical input of such spectrometers.
2. Description of the Prior Art
In the majority of prior art spectrometers, a quantity of sample is placed in a fixed position in an excitation device and heated until it is consumed. For reference, a variety of flame and non-flame excitation devices exist. Among the non-flame devices are arcs and plasma jets, illustrations of which are shown, for example, in U.S. Pat. Nos. 4,009,413, Elliot et al., and 4,147,957, Hildebrand. Inductively coupled plasma furnaces are also widely used.
In the above devices, the sample quantity and position and consequently the duration of excitation per sample remain fixed and limited. In multi-element analysis, it is often necessary to measure the intensity of a number of different wave lengths which appear in various spatial positions at the output focal plane. Time will therefore limit the number of such measurements which can be made for a single sample before the sample is consumed.
One solution to the problem of limited excitation time is to photograph the entire output spectrum of the short duration excitation for later analysis. Another is to reintroduce further specimens of the same sample and repeat the excitation and measurement process at different wave lengths. Another is to employ an array of detectors, spatially arranged to simultaneously measure a plurality of wavelengths.
The invention disclosed herein, in contrast to the above prior art devices, allows a continuous measurement and analysis to be carried out. This is accomplished by depositing a dissolved sample contained in a liquid or solvent uniformly over a uniform transport medium, preferably a length of filament, and then transporting the filament through the excitation situs of the spectrometer at a uniform rate. The filament is preferably, although not necessarily, electrically conductive and of a configuration to which the sample solution will adhere well and in some quantity.
It is a substantial advantage to be able to carry out continuous analysis as consecutive uniform portions of a sample are presented to the spectrometer. For example, a plurality of programmed scans by the spectrometer photodetection system may be conducted to determine the presence or absence of a number of elements. Additionally, background noise corrections may be made intermittently between scans. A high rate of sampling of the products of industrial processes including pollutants may be carried out and a complete, quantitative and qualitative analysis of each sample concluded on an automatic or semi-automatic basis. Errors which may occur when reintroducing samples in prior art fixed systems are eliminated.